1. Field of the Invention
This invention relates to a method and apparatus for washing and cleaning workpieces. More particularly, this invention pertains to a method and apparatus for washing and cleaning metal castings and machined parts to remove all types of contaminants such as rust, oils, stains, paints or other coatings, chips, burrs, particles and oxides to meet stringent part cleanliness specifications.
2. State of the Prior Art
The machines and methods for cleaning or washing articles or parts are extremely diverse, and even in the field of metal workpieces, primarily in the form of castings, forgings, extrusions and machined parts, such multiform processes and equipment pervades the various industries.
High pressure streams of abradant and liquids are commonly used separately or in combinations. Shot blasting or sand blasting with various types of abrasive particles typifies a dry abradant process; whereas, steam cleaning or high pressure jet impingement is representative of high pressure liquid cleaning.
Other processes and equipment rely on circulation of abradant and liquids such as in the use fluidized beds of abrasive particles or in submerged solvent washers.
Most often, multi-stage processing is required to meet even minimum industry standards, and in space age and intricately machined automotive valve and engine block components, sequential cleaning has been a virtual necessity.
Multi-stage equipment utilizing combinations of various types of machines are still in common use; for example, using barrel-finishing, wire brushing, buffing and solvent immersion. A recently developed process utilizes an intermittent operating conveyor with workpieces being serially conveyed to sequential grinding or deburring stations in which rotary reciprocating tools engage the workpiece followed by gyro-finishing apparatus in which the workpieces are chucked and rotated while being submerged in an abrasive media.
Various batch-type equipment have been developed combining solid abrasive particles with cleaning fluid. Typically, smaller workpieces are tumbled in drums and larger workpieces are subjected to jet blasts with a high velocity liquid carrying an abrasive grit, the liquid often being tailored to include an appropriate solvent or surfactant.
In other batch equipment, larger and smaller parts can be processed where the abrasive media and liquid is vibrated or subjected to a turbulent flow such as by the use of centrifugal force while the part or parts are immersed in the media-liquid.
In still another batch type of operation, the parts are vibrated while the abrasive media and liquid are cascaded through a working chamber. A primary problem with this latter type of equipment and some of the other equipment where the media-liquid is vibrated is that the chamber and other equipment parts along with any fixturing is subjected to the abrasive action of the media so as to be a major maintenance-equipment replacement problem.